1. Field of the Invention
This invention pertains generally to electrical connectors employing layered elastomeric strips consisting essentially of a plurality of mutually parallel layers of alternately conductive and non-conductive elastomer and sold by the assignee of this application under the trademark ZEBRA. The invention particularly pertains to retainers and supports for layered elastomeric electrical connectors of this general class.
2. Description of the Prior Art
In recent years, particularly with the substantial reduction in physical dimensions of electronic components such as LED and LCD alpha-numeric displays, integrated circuits, and the like, the use of electrical connectors employing stamped metal contacts has begun to give away to a class of electrical connectors employing electrically conductive elements which are not wholly metallic. A particularly useful layered elastomeric connector was disclosed in Ser. No. 468,651 filed May 10, 1974, now abandoned, which consisted essentially of a plurality of mutually parallel layers of alternately conductive and nonconductive elastomer. Similar layered connectors are to be found in published Japanese Patent Applications Sho 49-765 and Sho 47-25523. A connector of this general class has been sold under the trademark ZEBRA by the assignee of the present application. The generic term layered elastomeric connector has been adopted to refer to this general class of electrical connectors.
When the layered elastomeric connector was first introduced, problems directly associated wth contact potentials developing between the connector itself and the electrically conductive areas sought to be connected arose. It was first generally assumed that to overcome such problems, one merely increased the contacting area of the elastomeric connector, thereby affording a greater probability of eliminating this undesirable contact potential. This solution yielded yet additional problems principally related to surface smoothness and linearity of the connector as well as to durometer of the elastomers employed since an increase in contact area results in a corresponding increase in the total force required to connect electrical components thereto. In situations such as that illustrated in U.S. Pat. No. 3,885,173, it had been the general practice to form a self-supporting layered elastomeric connector in the form of a strip or ribbon which connects a number of mating electrically conductive areas. In order that the strip or ribbon be self-supporting, the width of the elastomeric strip or ribbon was usually equal to or greater than the dimension of separation between the two sets of electrically conductive areas sought to be connected. Since the total force which could be applied to many electrical components is rather restricted due to the materials used in their construction, the contact pressures between the elastomeric connector and the electrically conductive areas sought to be connected was rather low, and as a result, satisfactory performance was not always achieved.
It was subsequently discovered that an increase in performance reliability of layered elastomeric connectors could be achieved by simply reducing the contact area thereby increasing the contact pressure between the elastomeric electrical connector and the electrically conductive areas sought to be connected. A reduction in contact area could only be achieved by a substantial reduction in width of the connector strip or ribbon while maintaining the same separation between the two sets of electrically conductive areas sought to be connected. The ratio of separation distance to strip width has been adopted to define a dimensionless number referred to by the term aspect ratio. While layered elastomeric connectors were originally introduced having an aspect ratio in the neighborhood of 1 or even less than 1, it has now been learned that aspect ratios greater than 2 and preferably about 3 or 4 are preferred. While increased performance reliability for such a layered elastomeric connector is achieved, the layered elastomeric electrical connector is no longer self-supporting and some means for supporting the connector is necessary. One such support means is to be found in U.S. Pat. No. 3,998,512 which discloses simply a relatively rigid plastic support strip which supports an elastomeric connector having a very small width dimension. The support strip permitting the necessary compression of the elastomeric connector only through a very minor portion of the connector. Other examples of the prior art are to be found in U.S. Pats. No. 3,895,413, 3,998,513, 4,012,117, and Application Ser. No. 846,344 filed Oct. 28, 1978 entitled Retainer for the Elastomeric Electrical Connector.
A common failing of the prior art supports for layered elastomeric connectors is the reliance entirely on the elastomeric character of the layered elastomeric connector to compensate for variations in surface smoothness and linearity of the surfaces sought to be connected. While reliance was often placed on softer durometer elastomers, this has not always proved to be a satisfactory solution. It is therefore an object of the present invention to provide support means which incorporates features which respondto inherent variations in surface smoothness and linearity which might otherwise exceed the elastic deformation ability of the layered elastomeric connector.